Segment:
Mid-size Luxury Sedan/Wagon
Target Audience:
Affluent consumers seeking robust, reliable, and comfortable transportation with a focus on diesel efficiency and build quality.
Key Competitors:
BMW 5 Series (E28), Audi 100/200, Volvo 240/260, Cadillac Seville, Lincoln Continental.
Distinctive Attributes:
Legendary Mercedes-Benz build quality and durability, the robust and fuel-efficient OM617 turbocharged diesel engine, comfortable and spacious interior, advanced safety features for its time, sophisticated ride quality.
Manual Value Proposition:
Provides authorized diagnostic and repair procedures directly from the manufacturer, ensuring accuracy and completeness for maintaining these classic vehicles.
Powertrain:
Engine (OM617, 3.0L Turbo Diesel), Fuel System (Injection Pump, Injectors, Glow Plugs), Exhaust System, Cooling System, Lubrication System.
Drivetrain:
Transmission (Automatic 4-speed, likely 722.1), Clutch (if applicable to manual variants, though 300TD was predominantly automatic), Driveshafts, Differentials.
Chassis:
Suspension (Front Independent, Rear Independent Swing Axle), Steering System (Recirculating Ball Power Steering), Brakes (Hydraulic, Front Disc, Rear Drum or Disc depending on year/market), Wheels and Tires.
Electrical:
Battery, Charging System (Alternator), Starting System, Ignition System (Diesel Pre-glow), Lighting System, Gauges and Instruments, Wiper/Washer System, HVAC Controls, Power Accessories (Windows, Locks, Antenna).
Body:
Body structure, Doors, Hood, Trunk, Bumpers, Glass, Seals, Interior Trim, Seats.
Maintenance:
Oil Changes, Filter Replacements (Oil, Fuel, Air), Fluid Level Checks and Top-offs, Belt Adjustments and Replacements, Brake Pad/Shoe Replacement, Spark Plug/Glow Plug Checks.
Troubleshooting:
Diagnostic procedures for common starting issues, engine performance problems, electrical faults, and drivability concerns, likely utilizing symptom-based charts.
Repair Overhaul:
Detailed step-by-step instructions for component disassembly, repair, reassembly, and adjustment, including engine rebuild, transmission overhaul, suspension component replacement, brake system repair, and electrical component replacement.
Specifications Data:
Torque specifications for critical fasteners, diagnostic data (e.g., injection timing, valve clearances, compression ratios), fluid capacities, lubrication points, and wiring diagrams.
Depth:
Comprehensive, covering everything from basic routine maintenance to complete engine and transmission overhauls, advanced electrical diagnostics, and bodywork repairs. Suitable for professional technicians and experienced DIY enthusiasts.
Engine Type:
Inline 5-Cylinder, Naturally Aspirated (later turbocharged)
Engine Code:
OM617.912 (for 300TD in this era, turbocharger common)
Displacement:
3.0 Liters (2998 cc)
Bore X Stroke:
87.0 mm x 100.0 mm
Compression Ratio:
21.0:1 (approximate)
Horsepower:
Approx. 80-85 hp (naturally aspirated), Approx. 110-125 hp (turbocharged, depending on specific market and year).
Torque:
Approx. 130-140 lb-ft (naturally aspirated), Approx. 170-180 lb-ft (turbocharged, depending on specific market and year).
Injection System:
Bosch Mechanical Inline Injection Pump and Injectors
Air Intake:
Naturally Aspirated or Turbocharged with Intercooler (later models).
Cooling Type:
Liquid Cooled
Oil Capacity:
Approx. 7.5 liters (with filter)
Transmission Type:
4-Speed Automatic (Model 722.1)
Optional Transmission:
5-Speed Manual (less common on 300TD, more prevalent on 300D sedan).
Automatic Features:
Torque Converter Lock-up (on some later models), Hydraulic Control.
Automatic Transmission Fluid:
MB Specification 236.1 (e.g., Dexron II compatible, but always check manual for exact spec).
Body Styles:
Sedan (W123), Wagon (S123)
Length:
Sedan: ~187.0 in (4750 mm), Wagon: ~191.7 in (4870 mm)
Width:
Approx. 69.5 in (1765 mm)
Height:
Sedan: ~55.7 in (1415 mm), Wagon: ~56.7 in (1440 mm)
Curb Weight:
Approx. 3400-3700 lbs (1540-1680 kg), depending on body style and equipment.
Historical Ratings:
While official NHTSA ratings were not as standardized as today, Mercedes-Benz of this era was known for robust safety engineering and crashworthiness for its time.
Active Safety:
Four-wheel disc brakes (on some later models, otherwise front disc/rear drum), Power steering, Anti-lock Braking System (ABS) became available on later W123 models.
Passive Safety:
Reinforced passenger compartment, crumple zones, padded dashboard, safety belts (three-point front, two-point rear initially, evolving to three-point rear), dual-pane safety glass.
Audio System:
Factory AM/FM radio, optional cassette player. Limited integration by modern standards, but functional for its era.
Early Systems:
Cruise control (optional), power windows, power locks, power antenna, rear window defroster, intermittent wipers.
Connectivity Features:
None by modern definition. Analog systems and mechanical controls were prevalent.
Oil Change Interval:
Typically every 3,000-5,000 miles or 6 months, depending on driving conditions and oil used (refer to manual for specific recommendations).
Fuel Filter Interval:
Recommended replacement at 15,000-30,000 miles or annually, crucial for diesel longevity.
Air Filter Interval:
Every 15,000-30,000 miles or as needed based on driving environment.
Transmission Service Interval:
Fluid and filter change typically every 30,000-50,000 miles.
Engine Oil:
API CD or higher, SAE 15W-40 or 10W-40 diesel-specific oil (refer to manual for precise viscosity and spec).
Coolant:
Ethylene glycol-based antifreeze, 50/50 mix with distilled water. MB Specification 325.0 or equivalent.
Power Steering Fluid:
MB Specification 236.3 (e.g., Pentosin CHF 11S or compatible fluid).
Common Problems:
Vacuum leaks (affecting central locking, climate control, engine idle), injector pump seals, glow plug system issues, timing chain wear (though generally robust), front suspension bushings, rust (especially in lower body panels, wheel wells, and rocker panels).
Diesel Specific Concerns:
Fuel filter clogging, injector needle sticking, necessitating proper fuel quality and regular filter changes.
Mercedes Benz Legacy:
Founded on innovation and engineering excellence, Mercedes-Benz has a long history of producing durable, luxurious, and technologically advanced vehicles.
W123 Lineage:
The W123 chassis replaced the W114/W115 'Stroke Eight' models. The 300TD wagon, introduced in 1977, was a significant addition, offering luxury diesel utility.
Manufacturing Location:
Primary production in Germany (Sindelfingen), with some assembly in other global locations.
Sales Success:
The W123 platform was a massive global success, renowned for its durability and reliability, particularly the diesel variants.
